diff --git a/minifier.js b/minifier.js
index 25c0177175..a83069ab85 100644
--- a/minifier.js
+++ b/minifier.js
@@ -17,13 +17,21 @@ Minifier.js.minify = function (scripts, minify, callback) {
 	});
 
 	async.filter(scripts, function (script, next) {
-		file.exists(script, function (exists) {
+		file.exists(script, function (err, exists) {
+			if (err) {
+				return next(err);
+			}
+			
 			if (!exists) {
 				console.warn('[minifier] file not found, ' + script);
 			}
-			next(exists);
+			next(null, exists);
 		});
-	}, function (scripts) {
+	}, function (err, scripts) {
+		if (err) {
+			return callback(err);
+		}
+		
 		if (minify) {
 			minifyScripts(scripts, callback);
 		} else {
diff --git a/package.json b/package.json
index a9dbdfb82b..f80a1b12c9 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
     "coveralls": "istanbul cover _mocha --report lcovonly -- -R dot && cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js && rm -rf ./coverage"
   },
   "dependencies": {
-    "async": "~1.5.0",
+    "async": "^2.1.4",
     "autoprefixer": "^6.2.3",
     "bcryptjs": "~2.3.0",
     "body-parser": "^1.9.0",
diff --git a/src/file.js b/src/file.js
index df820cc47f..a231ddd01d 100644
--- a/src/file.js
+++ b/src/file.js
@@ -87,19 +87,27 @@ file.allowedExtensions = function () {
 
 file.exists = function (path, callback) {
 	fs.stat(path, function (err, stat) {
-		callback(!err && stat);
+		if (err) {
+			if (err.code === 'ENOENT') {
+				return callback(null, false);
+			}
+			return callback(err);
+		}
+		return callback(null, true);
 	});
 };
 
 file.existsSync = function (path) {
-	var exists = false;
 	try {
-		exists = fs.statSync(path);
-	} catch(err) {
-		exists = false;
+		fs.statSync(path);
+	} catch (err) {
+		if (err.code === 'ENOENT') {
+			return false;
+		}
+		throw err;
 	}
 
-	return !!exists;
+	return true;
 };
 
 module.exports = file;
diff --git a/src/meta/dependencies.js b/src/meta/dependencies.js
index 3f892c37ab..fdfa755198 100644
--- a/src/meta/dependencies.js
+++ b/src/meta/dependencies.js
@@ -19,14 +19,17 @@ module.exports = function (Meta) {
 
 		winston.verbose('Checking dependencies for outdated modules');
 
-		async.every(modules, function (module, next) {
+		async.each(modules, function (module, next) {
 			fs.readFile(path.join(__dirname, '../../node_modules/', module, 'package.json'), {
 				encoding: 'utf-8'
 			}, function (err, pkgData) {
-				// If a bundled plugin/theme is not present, skip the dep check (#3384)
-				if (err && err.code === 'ENOENT' && (module === 'nodebb-rewards-essentials' || module.startsWith('nodebb-plugin') || module.startsWith('nodebb-theme'))) {
-					winston.warn('[meta/dependencies] Bundled plugin ' + module + ' not found, skipping dependency check.');
-					return next(true);
+				if (err) {
+					// If a bundled plugin/theme is not present, skip the dep check (#3384)
+					if (err.code === 'ENOENT' && (module === 'nodebb-rewards-essentials' || module.startsWith('nodebb-plugin') || module.startsWith('nodebb-theme'))) {
+						winston.warn('[meta/dependencies] Bundled plugin ' + module + ' not found, skipping dependency check.');
+						return next();
+					}
+					return next(err);
 				}
 
 				try {
@@ -34,20 +37,24 @@ module.exports = function (Meta) {
 				} catch(e) {
 					process.stdout.write('[' + 'missing'.red + '] ' + module.bold + ' is a required dependency but could not be found\n');
 					depsMissing = true;
-					return next(true);
+					return next();
 				}
 
 				var ok = !semver.validRange(pkg.dependencies[module]) || semver.satisfies(pkgData.version, pkg.dependencies[module]);
 
 				if (ok || (pkgData._resolved && pkgData._resolved.indexOf('//github.com') !== -1)) {
-					next(true);
+					next();
 				} else {
 					process.stdout.write('[' + 'outdated'.yellow + '] ' + module.bold + ' installed v' + pkgData.version + ', package.json requires ' + pkg.dependencies[module] + '\n');
 					depsOutdated = true;
-					next(true);
+					next();
 				}
 			});
-		}, function (ok) {
+		}, function (err) {
+			if (err) {
+				return callback(err);
+			}
+			
 			if (depsMissing) {
 				callback(new Error('dependencies-missing'));
 			} else if (depsOutdated) {
diff --git a/src/meta/themes.js b/src/meta/themes.js
index be48d1e70d..777e1af5df 100644
--- a/src/meta/themes.js
+++ b/src/meta/themes.js
@@ -27,18 +27,28 @@ module.exports = function (Meta) {
 			async.filter(files, function (file, next) {
 				fs.stat(path.join(themePath, file), function (err, fileStat) {
 					if (err) {
-						return next(false);
+						if (err.code === 'ENOENT') {
+							return next(null, false);
+						}
+						return next(err);
 					}
 
-					next((fileStat.isDirectory() && file.slice(0, 13) === 'nodebb-theme-'));
+					next(null, (fileStat.isDirectory() && file.slice(0, 13) === 'nodebb-theme-'));
 				});
-			}, function (themes) {
+			}, function (err, themes) {
+				if (err) {
+					return callback(err);
+				}
+
 				async.map(themes, function (theme, next) {
 					var config = path.join(themePath, theme, 'theme.json');
 
 					fs.readFile(config, function (err, file) {
 						if (err) {
-							return next();
+							if (err.code === 'ENOENT') {
+								return next(null, null);
+							}
+							return next(err);
 						}
 						try {
 							var configObj = JSON.parse(file.toString());
diff --git a/src/plugins.js b/src/plugins.js
index b8ddbdc0fe..52378e7f38 100644
--- a/src/plugins.js
+++ b/src/plugins.js
@@ -161,9 +161,7 @@ var middleware;
 				});
 
 				// Filter out plugins with invalid paths
-				async.filter(paths, file.exists, function (paths) {
-					next(null, paths);
-				});
+				async.filter(paths, file.exists, next);
 			},
 			function (paths, next) {
 				async.map(paths, Plugins.loadPluginInfo, next);
@@ -346,7 +344,13 @@ var middleware;
 
 				async.filter(dirs, function (dir, callback) {
 					fs.stat(dir, function (err, stats) {
-						callback(!err && stats.isDirectory());
+						if (err) {
+							if (err.code === 'ENOENT') {
+								return callback(null, false);
+							}
+							return callback(err);
+						}
+						callback(null, stats.isDirectory());
 					});
 				}, function (plugins) {
 					next(null, plugins);
diff --git a/src/plugins/load.js b/src/plugins/load.js
index 60d584f99f..98a470f914 100644
--- a/src/plugins/load.js
+++ b/src/plugins/load.js
@@ -31,9 +31,7 @@ module.exports = function (Plugins) {
 					return path.join(__dirname, '../../node_modules/', plugin);
 				});
 
-				async.filter(plugins, file.exists, function (plugins) {
-					next(null, plugins);
-				});
+				async.filter(plugins, file.exists, next);
 			},
 		], callback);
 	};
diff --git a/src/privileges/helpers.js b/src/privileges/helpers.js
index 9df9d8cd7b..02e1bed879 100644
--- a/src/privileges/helpers.js
+++ b/src/privileges/helpers.js
@@ -8,12 +8,8 @@ var helpers = {};
 
 helpers.some = function (tasks, callback) {
 	async.some(tasks, function (task, next) {
-		task(function (err, result) {
-			next(!err && result);
-		});
-	}, function (result) {
-		callback(null, result);
-	});
+		task(next);
+	}, callback);
 };
 
 helpers.isUserAllowedTo = function (privilege, uid, cid, callback) {
diff --git a/src/rewards/index.js b/src/rewards/index.js
index 4ba403fce8..398abfb8f3 100644
--- a/src/rewards/index.js
+++ b/src/rewards/index.js
@@ -37,12 +37,14 @@ rewards.checkConditionAndRewardUser = function (uid, condition, method, callback
 		function (rewards, next) {
 			async.filter(rewards, function (reward, next) {
 				if (!reward) {
-					return next(false);
+					return next(null, false);
 				}
 
-				checkCondition(reward, method, next);
-			}, function (eligible) {
-				if (!eligible) {
+				checkCondition(reward, method, function (result) {
+					next(null, result);
+				});
+			}, function (err, eligible) {
+				if (err || !eligible) {
 					return next(false);
 				}